diff --git a/include/wx/msw/tooltip.h b/include/wx/msw/tooltip.h
index 8b7f805f1a..41855799d9 100644
--- a/include/wx/msw/tooltip.h
+++ b/include/wx/msw/tooltip.h
@@ -35,6 +35,7 @@ public:
     void RelayEvent(WXMSG *msg);
 
 private:
+    static HWND hwndTT;
     // create the tooltip ctrl for our parent frame if it doesn't exist yet
     // and return its window handle
     WXHWND GetToolTipCtrl();
@@ -45,4 +46,3 @@ private:
     wxString  m_text;           // tooltip text
     wxWindow *m_window;         // window we're associated with
 };
-